1. Field of the Invention
The invention relates to an apparatus for detecting video signals, and more particularly, to a device for detecting sawtooth artifact and/or field motion of video signals.
2. Description of the Prior Art
In interlaced scan, odd scan lines and even scan lines of a frame are scanned in sequence. Thus, each frame is actually composed of an even field and an odd field.
In progressive scan, the two fields are combined into one frame, and then the frame is scanned at double horizontal scan frequency in sequence, so that the quality of the display image is improved.
Because a time difference exists between different fields, when combining two fields into one frame, it is important to detect whether there is image motion between the two fields to be combined, that is, whether there is field motion. If field motion exists, a sawtooth artifact appears in the frame after combining two fields, and the quality of the image decreases.
However in the prior art, the method for detecting field motion and the method for detecting the sawtooth artifact are different (cf. U.S. Pat. No. 6,580,463). Furthermore these methods are actually too complicated to implement.